Cyclization of Chalcone Derivatives: Design, Synthesis, In Silico Docking Study, and Biological Evaluation of New Quinazolin-2,4-diones Incorporating Five-, Six-, and Seven-Membered Ring Moieties as Potent Antibacterial Inhibitors

Four novel series of quinazolin-2,4-diones bearing five-, six-, and seven-membered heterocyclic moieties 2-14 (such as pyrazole, oxazole, pyrimidine, and azepines) through the 1,4-phenyl linkage were designed, synthesized, and evaluated in terms of their antibacterial activities. Analytical and spectral techniques (FT-IR, 1H NMR, 13C NMR, and Mass) were utilized for the structural elucidation of all of the synthesized compounds 2-14. Furthermore, the potential antibacterial activity of the thirteen compounds was further evaluated in vitro against two different Gram-negative G-ve bacterial strains (named Escherichia coli ATCC 25955, Pseudomonas aeruginosa ATCC 10145) and two Gram-positive G+ve bacterial strains (named Bacillus subtilis ATCC 6633 and Staphylococcus aureus NRRL B-767). Investigation of the antibacterial potential indicated that the newly synthesized compounds, especially 13, exhibited remarkable antibacterial activity against pathogens, comparable to the standard drug ciprofloxacin (a known potent antibacterial agent). Additionally, compounds 2-14 and ciprofloxacin were assessed in silico using molecular docking studies against the target thymidine phosphorylase enzyme (PDB ID: 4EAD). Moreover, the structure activity relationship (SAR) for these compounds was also described to give guidance about the effective molecules that could play an important role in identifying potential antibacterial agents. Finally, the drug-likeness and physicochemical parameters of the newly synthesized molecules 2-14 were in silico investigated. Among them, we found that the compound 3-[4-(6-phenyl-6,7-dihydro-5-oxa-9-aza-benzocyclohepten-8-yl)-phenyl]-1H-quinazolin-2,4-dione 13 with the highest binding affinity showed a strong fit to the active site of the tested enzyme, indicating 13 as a promising drug candidate for designing and developing novel classes of antibiotics.

One-Pot Synthesis of Unprotected 2-Acylpyrroles from 1,2,3-Triazoles and 2-Hydroxymethylallyl Carbonates

An efficient, tandem one-pot approach to synthesize multisubstituted 2-acylpyrroles from readily prepared N-tosyl triazoles and 2-hydroxymethylallyl carbonates is reported. The reaction proceeds via Rh(II)-catalyzed O-H insertion, [3,3]-sigmatropic rearrangement, Pd(0)-catalyzed oxidative addition, intramolecular cyclization, DBU-promoted E1cB elimination, double bond isomerization, and aromatization, enabling the disconnection and formation of multiple bonds in one reactor. The approach represents a highly regioselective way to access di-, tri-, and tetra-substituted NH pyrroles with high efficiency.

Catalyst-free direct regiospecific multicomponent synthesis of C3-functionalized pyrroles

An operationally simple catalyst-free protocol for the direct regiospecific synthesis of β-(C3)-substituted pyrroles has been developed. The enamine intermediate, in situ generated from succinaldehyde and a primary amine, was trapped with activated carbonyls before the Paal-Knorr reaction in a direct multicomponent "just-mix" fashion to furnish pyrroles with overall good yields. Several C3-substituted N-alkyl/aryl/H pyrroles have been produced under open-flask conditions with high atom economy and avoiding protection-deprotection chemistry.

Transition metal free, green and facile halogenation of ketene dithioacetals using a KX–oxidant system

A facile oxidative halogenation of α-oxo ketene dithioacetals is achieved by using a potassium halide and an oxidant combination under transition metal free conditions at ambient temperature.

Synthesis of Sulfamate-Fused 2-Aminopyrroles via an Isocyanide-Based Three Component [1+2+2] Annulation

An efficient preparation of sulfamate-fused 2-aminopyrroles was achieved through an isocyanide-based three-component [1+2+2] annulation of isocyanides, dialkyl acetylenedicarboxylates, and sulfamate-derived cyclic imines in good to excellent yields (up to 99 %). This reaction proceeds smoothly without any activation or modification of substances under neutral and metal-free conditions. The reaction could also be conveniently performed on a gram scale.

Metal free, facile sulfenylation of ketene dithioacetals catalyzed by an HBr–DMSO system

A transition metal free, efficient, sulfenylation of ketene dithioacetals catalyzed by an HBr–DMSO system is achieved. This strategy employs inexpensive and readily available HBr and DMSO to provide a direct C–H bond sulfenylation with a broad range of aryl thiols. This sulfenylated product is also transformed for the synthesis of pyrazole derivatives in excellent yield.

Metal-Free Vinyl C-H Sulfenylation/Alkyl Thiolation of Ketene Dithioacetals for the Synthesis of Polythiolated Alkenes

The sulfenylation of the vinyl C-H bond in ketene dithioacetals leading to the synthesis of polythiolated alkenes is achieved via the promotion of molecular iodine. In addition, alkyl thiols also exhibit tolerance to the C-H bond elaboration reaction for the synthesis of corresponding alkylthiolated ketene dithioacetals.

One-pot sequential multicomponent reaction between in situ generated aldimines and succinaldehyde: facile synthesis of substituted pyrrole-3-carbaldehydes and applications towards medicinally important fused heterocycles

An efficient sequential multi-component method for the synthesis of N-arylpyrrole-3-carbaldehydes has been developed. This reaction involved a proline-catalyzed direct Mannich reaction-cyclization sequence between succinaldehyde and in situ generated Ar/HetAr/indolyl-imines, followed by IBX-mediated oxidative aromatization in one-pot operation. The practical utility of this procedure is shown at gram-scale and the synthesis of diverse bioactive fused heterocyclic scaffolds such as pyrroloquinoline, pyrrolo-oxadiazole, dihydro pyrroloquinoline, and pyrrolo-phenanthridine.

Synthesis of fused cyanopyrroles and spirocyclopropanes via addition of N-ylides to chalconimines

DABCO-ylides react as a one-carbon source with chalconimines to afford fused cyanopyrrolesvia[4 + 1] annulation and spirocyclopropanesvia[2 + 1] annulation.

Active methylenes in the synthesis of a pyrrole motif: an imperative structural unit of pharmaceuticals, natural products and optoelectronic materials

Pyrrole is one of the most important azaheterocycles, due to its wide range of applications in pharmaceuticals and optoelectronic materials, coupled with its utility as an intermediate in natural products.

Arylsulfonylmethyl isocyanides: a novel paradigm in organic synthesis

p-Tosylmethyl isocyanide (TosMIC), an α-acidic isocyanide has emerged as a privileged reagent to access biologically relevant fused heterocycles and some natural products like (−)-ushikulide A, variolin B, porphobilinogen and mansouramycin B.

Reaction of α-amido sulfones with functionalized nitrocompounds: a new two-step synthesis of N-alkoxycarbonyl-2,5-disubstituted pyrroles

N-Alkoxycarbonyl-2,5-disubstituted pyrroles can be readily prepared by a new two-step procedure involving a preliminary addition of nitro ketals to α-amido sulfones followed by an acid promoted ring closure of the obtained intermediates through a cascade process.